Fiber optics security system

Abstract

Closed loop fiber optic link means, transferring energy from a radiant source to a receiver, includes serially connected fiber optic links and detectors. Energy cessation causes alarm. Detectors include: (1) A pair of optical transducers oriented whereby light, air transmitted, is received with insignificant loss. In water, light received is so insignificant that energy to the receiver ceases. The first transducer provides a light beam within a constant index of refraction medium to the second transducer spaced and oriented to ordinarily receive the light beam. When light passes through media having different refraction indices at non-normal angles, light is refracted whereby receiver energy ceases. The transducers are oriented in a straight inclined path. (2) Optical fiber, stable to approximately 135° F., which melts above approximately 155° F., provides fire detection. (3) A bimetallic element attached to one of axially aligned optical fiber holders, when heated, mis-align the fibers. A snap action bimetal device displaces at a specific temperature. (4) A connector holds optical fiber and condensing lens for narrow light beam emergence. A second connector, holding the end of a second fiber in proximity to a second lens focus, is axially aligned with the first so that the second fiber transmits light. Opaque objects therebetween interrupt the beam causing energy cessation. (5) Opening of an entrance device having optical fibers coupled in axial alignment to opposite sides thereof causes the fibers to mis-align, causing energy interruption. The radiant energy source and receiver are in proximity to each other.

What is claimed is: 
     
       1. A fiber optics security system comprising a radiant energy source including a solid state source and means for pulsing said solid source at a repetition rate;   a radiant energy receiver including means for detecting radiant energy at said rate;   closed loop fiber optic link means having one end coupled to receive energy from said source and having an opposite end coupled to provide energy to said receiver, said fiber optic link means including, in serial connection, a plurality of fiber optic links and a plurality of detection means; and   means responsive to cessation of energy to said receiver for providing a signal; wherein one of said detection means comprises   a first optical fiber having a first end;   a second optical fiber having a first end;   first holding means for holding said first end of said first optical fiber;   second holding means for holding said first end of said second optical fiber in axial alignment with said first end of said first optical fiber; and   bimetallic element means attached to said second holding means, whereby   upon heating of said bimetallic element means, said bimetallic element means causes displacement of said second holding means, and, thus, causes displacement of said first end of said first optical fiber with respect to said first end of said second optical fiber.   
     
     
       2. The fiber optics security system as recited in claim 1 wherein said bimetallic element means includes a snap action bimetal device for causing displacement to occur at a specific temperature. 
     
     
       3. A fiber optic detector comprising a first optical transducer means; and   a second optical transducer means in alignment with said first optical transducer means, and spaced a distance therefrom,   said distance being such that,   in air, light transmitted by said first optical transducer means is received by said second optical transducer means with insignificant loss, and   in water, light transmitted by said first optical transducer means encounters a significant loss due to the absorption characteristics of water whereby light received by said second transducer means is insignificant.   
     
     
       4. A fiber optic detector comprising a first optical fiber having a first end;   a second optical fiber having a first end;   first holding means for holding said first end of said first optical fiber;   second holding means for holding said first end of said second optical fiber in axial alignment with said first end of said first optical fiber; and   bimetallic element means attached to said second holding means, whereby   upon heating of said bimetallic element means, said bimetallic element means causes displacement of said second holding means, and, thus, causes displacement of said first end of said first optical fiber with respect to said first end of said second optical fiber.   
     
     
       5. The detector as recited in claim 4 wherein said bimetallic element means includes a snap action bimetal device for causing displacement to occur at a specific temperature.